1. Field of the Invention
The present invention relates to apparatus and methods for determining a state of a reformer for producing a reformed fuel to be supplied to an internal combustion engine by reforming a fuel air mixture.
2. Description of the Related Art
For example, Japanese Patent Application Laid-open No. 2002-54427 discloses an apparatus for adding a reformed gas (reformed fuel) containing CO and H2 to a fuel to be supplied to a combustion chamber of an internal combustion engine or an exhaust gas discharged from the combustion chamber. This apparatus includes a CO shift catalyst (reformer) in which a precious metal is carried by a carrier having an oxygen-absorption capacity. The CO shift catalyst reforms CO and H2O to H2 and CO2 by a water gas shifting reaction to produce a reformed gas containing CO and H2.
The Co shift catalyst deteriorates with the lapse of time. Thus, a concentration ratio between CO and H2 (CO/H2 concentration ratio) in the reformed gas produced by the CO shift catalyst also varies with the lapse of time, and a deterioration of an exhaust emission may be caused. Therefore, in the conventional apparatus, the oxygen absorption capacity of the CO shift catalyst is obtained from the oxygen concentration at a fluid inlet and a fluid outlet of the CO shift catalyst. Then, a state of the CO shift catalyst or the CO/H2 concentration ratio of the reformed gas relating to the degree of deterioration of the catalyst is estimated based on the obtained value indicating the oxygen absorption capacity. Further, an amount of the reformed gas to be added to the fuel or the exhaust gas of the internal combustion engine is determined based on the estimated CO/H2 concentration ratio.
However, it is not easy to precisely obtain the oxygen absorption capacity of the catalyst. Therefore, in the above-mentioned prior art, it is difficult to easily and precisely determine the state (the degree of deterioration or the abnormality) of the catalyst.